The field of the invention is that of rotatable turbine blades for hydroelectric generators.
Depending on their load, turbine blades are usually cast from steel or cast iron. Producing its finished shape requires a considerable expense for stock removal work. The mass forces caused by the great weight of these turbine blades must be allowed for in the design of the turbine blade adjustment apparatus. Also, a correspondingly high sealing pressure is applied in a guide apparatus formed by such blades. This achieves, with a sealed guide apparatus, a watertight closure in the area of the sealing edges of all turbine blades, despite manufacturing and assembly defects. Weight advantages are realized, though, when making the turbine blades from plate, according to another manufacturing process. Connected by welding, these plates have a better surface finish than castings, but such turbine blades also require a stock removal type processing in the area of the sealing edge.
U.S. Pat. No. 1,472,924 describes molding into the blade of a turbine made from steel or cast steel a groove that extends parallel with the turbine axis of rotation into which slot a strip from babbitt metal or wood is inserted. This achieves an improved sealing effect between the turbine blade contained in sealing position, in that the sealing edge of the adjacent turbine blade strikes against the inserted strip, and through its plastic deformation.
Also, West German Pat. No. 1,224,219 describes a turbine blade made in customary fashion where separate, attached seals are fastened to the fronts of the blade. These seals consist of a metallic core which is screwed to the turbine blade, and is provided with an inflatable envelope made of caoutchouc. In the closing position of the turbine blade, the seal is inflated. This makes contact with the components of the hydroelectric generator which border on the turbine blade, providing in this area a seal against the penetration of leakage water.
What is needed is a turbine blade which can be inexpensively produced. Specifically a turbine blade, which avoids stock removal type processing, is needed.